The American strike that killed Iranian Gen. Qasem Soleimani marks "an extremely serious and dangerous escalation of conflict in the Middle East with global significance" outgoing British opposition leader Jeremy Corbyn claims.

Soleimani led the Islamic Revolutionary Guard Corps' Quds Force. He and an Iraqi militia leader were killed in a drone strike Thursday near Baghdad's airport.

Corbyn, who was routed in recent British elections, called on the UK government to "urge restraint on the part of both Iran and the US, and stand up to the belligerent actions and rhetoric coming from the United States."

In a letter to Prime Minister Boris Johnson, Corbyn demanded a briefing of the Privy Council, the top advisory body to Queen Elizabeth II, about the Soleimani killing. Corbyn asked whether the Trump administration consulted with the British government before the strike and what advice was given. He also asked about precautions being taken to secure British nationals in the face of possible Iranian attacks.

Johnson called for restraint following the killing, but stated "we will not lament [Soleimani's] death" because of the thousands of innocent people and Western military personnel he had killed.

Corbyn has been strongly pro-Iran for more than a decade. Between 2009 and 2012 Corbyn accepted nearly $6,600 for appearances on the state-run Press TV outlet. He appeared on the channel even after the British government banned it.

He also has had a soft spot for Iran's terrorist proxies that Soleimani supported including Hizballah, Hamas and the Popular Front for the Liberation of Palestine (PFLP). Corbyn notoriously called Hizballah his "friends" during a 2009 parliamentary meeting, and his Labour Party argued last February that no clear evidence existed to designate it as a terrorist group.

Hamas backed Corbyn's election campaign, and an individual closely tied to the group running a pro-Corbyn website from Gaza, the Jerusalem Postreported.

"It seems his default position is to side with terrorists, with people like Hamas and Hezbollah, rather than side with our own agencies and military. That is historically what he has done," Labour Party House of Lords member Alan West said in November.